Why are covalent substances gases and liquid rather than solids?

Covalent compounds are held together with an intra molecular attraction which is weaker than metallic bond

hence covalent compounds exist as liquids, gases and soft solids

explanation:

venn diagram is pictorial representation with of circles showing the relation between two finite sets or things. the intersection part of two circles conveys the relation present in between those sets or things.

here in the venn diagram of sand and salt two circles represent sand and salt. but the area falling under the intersection of these circle represents the mixture of sand and salt.

so, in a venn diagram the mixture will be placed in a middle that is in between the intersection of two circles.